There exist robotic platforms for enhancing spine surgical procedures such as the SpineAssist™ system, as supplied by Mazor Surgical Technologies Ltd, of Caesarea, Israel. This system enables accurate spinal surgery to be readily performed with minimal intervention. Such systems can be used for guidance in pedicle screw insertion for spine fusion procedures. SpineAssist™ itself focuses on two key steps: Pre-operative planning of the surgical procedure to be performed and Intra-operative spatial positioning and orientation of surgical tools, such as a drill guide for drilling pedicle screw holes. Additional applications which can be performed using such systems include vertebroplasty, tumor evacuation, artificial disc placement, cervical and thoracic fusion procedures, and more. Additional applications of the robot used in the SpineAssist™ system have been described in U.S. Pat. No. 6,837,892, and in co-pending U.S. patent application Ser. Nos. 10/517,846, 10/557,048, 10/595,305, and in International Patent Application No. PCT/IL2006/000056 published as WO 2006/075331.
Computer aided surgery applications, such as the above described robotic systems, generally use a preoperative CT of the patient in order to perform the procedure planning. Acquiring a CT scan of a patient requires expensive resources that are not always present or available in hospitals. In addition, the need of a CT scan prior to the operation extends the overall time of the procedure, time which is not always available. Additionally, CT imagers, because of their size and weight, are almost invariably located in dedicated sites, and it is exceedingly rare to find a CT imager located in an operating room where the surgical procedure is being conducted. On the other hand, during the operation itself, it is possible to acquire X-ray fluoroscopic images using a mobile C-arm system, which is commonly present in the operation room. The SpineAssist™ platform, for instance, acquires and uses two such fluoroscopic images to align the CT on which the planning was done, with the patient position during the surgery. The alignment is done by means of a registration procedure using a known 3D target which is attached to the vertebra during the surgery, and whose position can be accurately determined in the fluoroscopic images.
Unfortunately, it would not be recommendable to perform the procedure planning using C-arm fluoroscopic images acquired in the operating room, due to the fact that only AP (anteroposterior), LT (lateral), or in-between angle images can be taken. AX (axial) images, which are important in the planning procedure, cannot be acquired using a mobile C-arm. The importance of the AX view for the preoperative planning is apparent from FIG. 1, which is a view of a control screen showing from an axial view, a pair of pedicle screws inserted into a vertebra. As is evident from here, only in an axial view is it possible to accurately view the intended position of the screws, to ensure that they do not cause damage to the spinal cord, or break out of the pedicle. Similar consideration apply to most surgical procedures, where the limitation of imaging in one plane only may be disadvantageous.
There therefore exists a need for generating AX views of the vertebrae or other surgical site, using a standard C-arm fluoroscope imaging system, without the need for an expensive CT system, and with the ability to conveniently generate such views during a surgical procedure. Such a system is called in this application a CT-free imaging system.
The disclosures of each of the publications mentioned in this section and in other sections of the specification are hereby incorporated by reference, each in its entirety.